* President has yet to announce re-election bid
* Santos, popularity sliding, waffles on next term
By Eduardo Garcia
BOGOTA, April 22 (Reuters) - Colombian President Juan Manuel Santos on Monday said he is no longer considering running for a shorter term of two years in 2014 and told lawmakers it was too early to consider an extension of presidential terms to six years.
Santos on Friday signaled he may seek re-election, but only if he can stay in office for two more years, half the usual term. He also said that from 2016 onwards, the presidential term should be extended to six years and that a president's right to stand for re-election should be scrapped.
That would have required Congress to amend the constitution.
The proposal was not well received by local media and the opposition, which prompted Santos to write a letter to the head of Congress saying that this is not the right time to extend the presidential mandate.
"I thought - wrongly, it seems - that a proposal of this nature would be well received by all, including the opposition, because it would not imply and automatic extension of my mandate ... But many did not understand it that way," the letter said.
"I consider that it would be inconvenient to push ahead with an initiative of this nature in Congress and that the debate should wait until the next government is elected," Santos said.
In the letter addressed to Congress president Roy Barreras Santos did not refer to his plans to run for another four-year term.
The 61-year-old must declare his candidacy six months before a May 2014 election, so around November, but poll numbers show support for Santos is shrinking, which means he probably needs to start gaining momentum now.
Santos was elected in August 2010 by a landslide thanks in part to the support of his then-boss, former President Alvaro Uribe, who is now the de-facto head of the opposition.
While Santos came to power promising to maintain Uribe's tough stance against Marxist rebels, the former defense minister took the biggest gamble of his political career when he began peace talks in November with the Revolutionary Armed Forces of Colombia, known as FARC.
The biggest risk for Santos' popularity are these ongoing negotiations to put an end to five decades of bloody war, which Santos wants completed this year.
"I want to take advantage of this opportunity to clarify that this discussion has nothing to do with the peace process," Santos said in the letter.
"Today, more than ever, I'm still thinking that to be successful this process should last months, not years."
The last attempt to negotiate an end to the war in 1999-2002 ended in shambles, but the FARC has been weakened after a decade-long U.S.-backed government offensive that has killed some top rebel leaders and pushed the group to remote areas.
If peace talks succeed this time, Santos's re-election would be all but clinched.
Opponents will try to capitalize on whatever comes out of the peace talks currently underway in Cuba, the slowing economy and social problems such as poverty. (Reporting by Eduardo Garcia)